This is a Shannon award providing partial support for the research projects that fall short of the assigned Institute's funding range but are in the margin of excellence. The Shannon award is intended to provide support to test the feasibility of the approach; develop further tests and refine research techniques; perform secondary analysis of available data sets; or conduct discrete projects that can demonstrate the PI's research capabilities or lend additional weight to an already meritorious application. The abstract below is taken from the original document submitted by the principal investigator. DESCRIPTION: The applicant proposes to investigate the role of the floorplate and notochord in dorso-ventral patterning of the vertebrate CNS. To address this question two different sets of experiments are proposed. First, the expression of genes normally restricted to dorsal parts of the neural tube (Wnt-1, Pax-3, msx-1, CRAPBI) will be redirected towards the floor plate. This will be achieved by generating transgenic mice in which the above mentioned genes are spatially regulated by a floor specific enhancer. Secondly, the same enhancer construct will be used to express either diptheria toxin or HSV-TK in the floor plate and thereby kill floor plate cells. In case of the HSV- TK the time of killing can be controlled temporally by administering the base analogue FIAU (which is required for the lethal effect of the virus) at the desired stage. In both sets of experiments, the effect of the manipulations on CNS development will be assayed using a large number of probes. These includes non specific histological examination, antibodies against specific cell types and molecular probes expressed in specific dorsal-ventral domains. It is expected that deletion of the floorplate lead to interpretable defects which shed light on the normal role of this structure in CNS patterning. Furthermore, the effect of misexpression of regulatory genes, such as Wnt-1 and Pax-3, may elucidate new aspects of the cellular function of these genes.